Field of the Invention
The present invention relates to a projection display apparatus which reduces adherence of fine foreign substances to a light modulation element.
Description of the Related Art
A projection display apparatus is provided with a plurality of heating elements in its inside. In order to cool these heating elements, for example, using a fan disposed inside the projection display apparatus, the air outside the projection display apparatus is taken in its inside and the air is introduced to the heating elements to be cooled. In this case, a lot of foreign substances such as dusts may float according to the environment of setting up the projection display apparatus. Therefore, a quality of a projection image may be deteriorated by the foreign substances intruded and adhering to an optical element provided inside the projection display apparatus when the cooling air is taken in its inside. Particularly, when the foreign substances adhere to an light modulation element, there is a problem that the foreign substances are easily visible in the projection image. On the other hand, the light modulation element needs to perform a position adjustment with respect to optical components housed inside the projection display apparatus and its performance is affected by stress due to an external force, and therefore it is difficult to adopt a solid sealed structure
Previously, a configuration in which a dust collection filter is disposed at an intake (air inlet), or a flexible dust-proof member such as a formed material having a small reaction force and a rubber is disposed around the optical element has been known. Japanese Patent Laid-open No. H11-305674 discloses a configuration in which a first dust-proof member is disposed between a light shielding plate and a base to which the light modulation element is attached and a second dust-proof member is disposed between a wave plate and the light shielding plate to ensure a high dust-proof property. Japanese Patent Laid-open No. 2004-020603 discloses a configuration in which a dust-proof cover is disposed between a light shielding member and a polarization beam splitter.
However, even in the configurations disclosed in Japanese Patent Laid-open Nos. H11-305674 and 2004-020603, there is a possibility that fine foreign substances are intruded through a gap in the dust-proof component. Particularly, it is difficult to ensure a sufficient dust-proof property (sealing property) for fine particles not greater than 1 μm for example, and dirt gradually adheres to the optical components due to the use for a long time and color unevenness may be displayed in the projection image.
When a filter which is provided with a small opening is used to capture the fine particles, a ventilation resistance of the filter increases and accordingly a noise of the fan increases and a size of an apparatus is enlarged. When the adherence or contact pressure is increased to improve the sealing property of each component, a dismantling property is deteriorated and the stress to the optical component is increased, and accordingly the optical performance is deteriorated and the position of the optical component is displaced.